Remote controls enable the user of a consumer electronic device to effectively operate that device from a distance without a tethered connection between the remote control and the device. Television sets have conventionally used remote controls for years. Other consumer electronic devices, for example, computers, interactive CD disc players, and stereo equipment, have also been utilized with remote controls.
Generally, conventional remote controls have utilized an infrared transmitter to generate a pulse train sent from the remote control to the receiver on the controlled device. Typically, each key corresponded to a unique sequence, most conventionally a binary sequence, which was transmitted to the receiver. FIG. 1 shows a prior art system for the representation of binary data. A three pulse train has a baseline level 10 at a first state and an "on" or high state at a second state. Pulse position modulation techniques conventional in the prior art utilize the time difference between the leading edges of pulses. As shown, a 600 microsecond +/-200 microsecond duration pulse 12 has a difference in time to the leading edge of pulse 14 of 1.22 ms +/-600 microseconds. This time difference represents a logic "0". The time difference between the leading edge of pulse 14 and pulse 16 is 2.44 ms +/-600 microseconds, representing a logic "1". A binary pulse train could be generated by sequentially forming pulses whose time delay from the preceding pulse were within one of the two time duration windows.
The ratio of the time difference for a logic 1 relative to a logic 0 is two. This ratio is relatively large, and is relatively unaffected by slight differences in clock speed between the clock or time base of the remote control and the clock or time base of the receiver. Deviation or drift in the clock rate rarely would have an impact upon the accuracy of the system.
Modern remote controls must transmit substantial amounts of information. Often times, a remote begins a transmission with a header identification of the type of remote, such as identifying a particular manufacturer and model of remote. The receiver may then use this information to decode the subsequent transmission. The most feature laden remote controls currently have hundreds, sometimes over 250, keys or states of control. Beyond the conventional modes of control, various higher data generating control devices, such as trackballs, have been incorporated in remote controls.
The demands placed upon remote controls by these new functionalities are underserved by the current transmission formats. Further, as the current formats are extended to address the higher data transfer requirements of current and future devices, the power consumption, and battery drain, increase. It is the object of this invention to provide a new data transmission format consistent with the increase in the quantity of data transmitted and to reduce power consumption.